Buckthorn was a rabbit who came to the Watership Down Warren from the Sandleford Warren. He was a strong rabbit who was going to join the Sandleford Owsla, when he reached full weight. He was described as a tough, sturdy rabbit with a quiet and easygoing nature. Like Silver, he is steadfast and dependable in a crisis.
He was injured by a rat while the group was resting in a barn following the ordeal in the Warren of Snares. Buckthorn, along with Holly, Strawberry, and Silver, went to Efrafa to ask if they could have a few does join their warren; he came back injured from a blow across the face. Following the Battle of Watership Down, he later joined the Watership Down Owsla.
Along with Bluebell, Acorn, and Speedwell, Buckthorn has not appeared in any of the adaptations of Watership Down.